With the rapid widespread use of computers and the start-up of digital broadcasting or the like, there have been demands for a hard disk drive with a higher capacity and a smaller diameter. For example, as a method for increasing the recording density of a memory hard disk used in the hard disk drive, it has been proposed that the unit recording area is decreased by lowering the flying height of a magnetic head. However, in order to lower the flying height of the magnetic head, the surface roughness, micro-waviness, etc. of the surface of a hard disk substrate should be correspondingly reduced. To meet these requirements, abrasive slurry capable of improving the surface characteristics of a substrate after polishing has been known (e.g., JP 2005-186269, JP 2006-518549, and JP 2007-168034).
In terms of improving both the productivity and the surface quality such as better smoothness and higher resistance to scratches, a method for manufacturing the hard disk substrate usually employs a multistage polishing system that includes two or more stages of polishing. In the final polishing process, i.e., the finish polishing process of the multistage polishing system, the substrate is generally polished with a finish polishing composition using colloidal silica particles so as to reduce the surface roughness and scratches. On the other hand, a polishing process (also referred to as a rough polishing process) prior to the finish polishing process is likely to use abrasive grains that have a relatively large particle size and can achieve a high polishing rate, e.g., alumina particles in terms of productivity.